JPH11255788A - Iron 0-valent complex, its production and production of tetralins - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a new iron 0-valent complex useful as a catalyst, or the like, for a regioselective partial hydrogenating reaction by reacting 1,2-bis(dicyclohexylphosphino)ethane iron (II) chloride complex with a sodium naphthalenide. SOLUTION: This new iron 0-valent complex is represented by formula I [Cy is cyclohexyl; R is a lower alkyl; (n) is an integer of 0-8] [e.g. Fe (η<6> - naphthalene)-1,2-bis(dicyclohexylphosphino)ethane] and is useful as a catalyst, or the like, for a regioselective partial hydrogenating reaction for simply producing tetralin (derivative) used as various industrial chemicals including solvents for coating materials, resins, oils and fats, or the like. The complex is produced by reducing an iron (II) chloride complex represented by formula II [dcype is 1,2-bis(dicyclohexylphosphino)ethane] with a sodium naphthalenide (derivative).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel iron zero-valent complex, a method for producing the same, and a method for producing tetralins using the iron zero-valent complex.

[0002]

2. Description of the Related Art Tetraline or its derivatives used as various industrial chemicals including solvents such as paints, resins, oils and fats are usually produced by hydrogenating naphthalene at a high temperature using a nickel catalyst. .

[0003]

However, in a hydrogenation reaction using a nickel catalyst, regioselective partial hydrogenation of naphthalene is difficult, and usually a large number of by-products are formed. There was a problem that a high temperature was required. An object of the present invention is to provide a novel iron zero-valent complex which enables a regioselective partial hydrogenation reaction of naphthalene or a derivative thereof and can easily produce tetralins (tetralin or a derivative thereof), a method of producing the same, and An object of the present invention is to provide a method for producing tetralins.

[0004]

Means for Solving the Problems The iron zero-valent complex of the present invention comprises:
Equation (1):

Embedded image (Where Cy represents a cyclohexyl group, R represents a lower alkyl group, and n represents an integer of 0 to 8), and a typical example thereof is Fe (η ⁶ -naphthalene) when n is 0.
(Dtype). Here, dtype is 1,2-bis (dicyclohexylphosphino) ethane,
That is, (C ₆ H ₁₁ ) ₂ PCH ₂ CH ₂ P (C ₆ H ₁₁ )
Abbreviation for ₂ .

[0005] The zero-valent iron complex of the present invention reacts with hydrogen at or near room temperature to enable regioselective partial hydrogenation of naphthalene or a derivative thereof to obtain the corresponding tetralin. That is, the method for producing tetralins of the present invention comprises reacting a zero-valent iron complex represented by the above formula (1) with hydrogen to form a compound represented by the following formula (2):

Embedded image (Wherein Cy, R and n are the same as described above), characterized by obtaining a complex having tetralins as a ligand.

The complex (2) is decomposed by heating or the like to obtain tetralins. Reaction is 5 to 40 atm
It is preferable to carry out at a hydrogen pressure of 0 to 50 ° C. Such a zero-valent iron complex of the present invention is obtained by converting an iron (II) chloride complex represented by the formula: FeCl ₂ (dtype) wherein dtype represents 1,2-bis (dicyclohexylphosphino) ethane. The compound can be produced by reduction with sodium naphthalenide represented by C ₁₀ H _8-n R _n Na (wherein R represents a lower alkyl group and n represents an integer of 0 to 8) or a derivative thereof. it can.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The lower alkyl group which may be substituted on the naphthalene ring in the iron-valent complex of the present invention includes, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group and tert-butyl group. Group, pentyl group,
Examples thereof include a straight-chain or branched alkyl group having 1 to 6 carbon atoms such as a hexyl group. Further, the substitution position and the substitution number of the substituent R are not particularly limited.

A zero-valent iron complex of the present invention represented by the above formula (1)
Is defined as Fe (η when n = 0 ⁶-Naphthalene)
(Dtype) is a typical example.
1 to 8 lower alkyl groups are substituted on the naphthalene ring
Derivatives. Hereinafter, Fe (η⁶-Naphthale
(Dtype) as an example, the iron zero-valent complex of the present invention.
Will be described.

As shown in the following reaction formula, Fe (η ⁶ -naphthalene) (dtype) relating to the iron zero-valent complex of the present invention represented by the formula (1a) is converted to a chloride represented by the formula (3). Obtained by reducing iron (II) complex with sodium naphthalenide.

Embedded image (In the formula, dtype and Cy are the same as described above.)

The amount of sodium naphthalenide added to the iron (II) chloride complex (3) may be in excess with respect to the complex (3), and is usually about 1 to 8 moles. The reaction is preferably performed in a solvent under an atmosphere of an inert gas such as nitrogen or argon gas. As the solvent, diethyl ether,
Diisopropyl ether, t-butyl methyl ether,
Examples include ethers such as tetrahydrofuran and 1,4-dioxane, which may be used as a mixture of two or more. Further, it is preferable that the solvent is previously subjected to dehydration and deoxygenation treatment.

In carrying out the above reduction reaction, the reaction temperature is not particularly limited, and the reaction proceeds even at room temperature.
Heating may be performed if necessary. Generally, the reaction temperature can be appropriately determined from the range of room temperature to about 50 ° C. The reaction time may be about 2 to 30 hours. The sodium naphthalenide to be used may be a derivative in which a lower alkyl group R is substituted on a naphthalene ring as shown in the above-mentioned general formula.
(II) can be reacted with the complex (3).

The product is purified by means of extraction, recrystallization, chromatography and the like. The iron (II) chloride complex
(3) can be obtained by reacting anhydrous iron (II) chloride with 1,2-bis (dicyclohexylphosphino) ethane (dtype). The reaction is carried out in an inert gas atmosphere in a solvent at 15 to
It is preferable to perform the reaction at 100 ° C., preferably 40 to 80 ° C., for 5 to 48 hours, preferably for about 10 to 30 hours.

The dtype is, for example, RJ Burt et.
al., J. Organomet. Chem., 182, 203 (1979). As the solvent, it is particularly preferable to use an aromatic hydrocarbon such as benzene, whereby the reaction proceeds quantitatively, and iron chloride is obtained in a high yield.
(II) Complex (3) can be obtained. Further, it is preferable that the solvent is previously subjected to dehydration and deoxygenation treatment as described above.

The produced iron (II) chloride complex (3) may be used as a starting material for producing the next iron zero-valent complex (1) without purification, but may be used as a purification means such as extraction and recrystallization. May be used for purification. In particular, when an aromatic hydrocarbon such as benzene is used as a solvent, the aromatic hydrocarbon may be removed from the product because the presence of the aromatic hydrocarbon may adversely affect the formation of a zero-valent iron complex. It is preferable to keep it.
The zero-valent iron complex (1) of the present invention reacts with hydrogen to cause regioselective partial hydrogenation of naphthalenes, thereby easily producing tetralins.

The reaction is carried out in an inert gas atmosphere under the condition of a zero-valent iron
(1) is dissolved in a solvent, and then the obtained solution is stirred under a predetermined hydrogen pressure. For example, the formula (1a)
When Fe (η ⁶ -naphthalene) (dtype) represented by the following formula is reacted with hydrogen to cause a partial hydrogenation reaction, the corresponding Fe (η ⁶ -tetralin) (dtype) is obtained.

Examples of the solvent include the above-mentioned ethers such as diethyl ether, diisopropyl ether, t-butyl methyl ether, tetrahydrofuran and 1,4-dioxane. The hydrogen pressure is 5 to 40.
atm, preferably about 10 to 30 atm. The reaction temperature may be room temperature, generally from 0 to 50.
It can be determined appropriately from the range of ° C. Reaction time is 5
It is good to be for about 50 hours, preferably about 10 to 30 hours. The generated Fe (η ⁶ -tetralin) (dcyp
e) After purification using a purification means such as extraction or recrystallization, tetralin can be obtained by heating in an appropriate solvent or the like. Also, when a tetralin derivative having a lower alkyl group as a substituent is obtained, a hydrogenation reaction can be carried out in the same manner as tetralin.

[0017]

EXAMPLES Hereinafter, the iron-valent complex of the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples. The solvents used in the following examples were all dehydrated and deoxygenated using sodium or potassium benzophenone ketyl as an indicator.

Reference Example [Synthesis of FeCl ₂ (dtype)] Anhydrous iron (II) chloride
(0.680 g, 5.37 mmol) and dtype
(2.44 g, 5.78 mmol) of benzene (49 m
L) The solution was heated to 70 ° C and stirred for 24 hours. Then, the mixture was filtered at room temperature with a filter paper and allowed to stand for 1 day. As a result, Fe containing one molecule of benzene per molecule
A pale purple needle of Cl ₂ (dtype) was obtained from the reaction mixture (3.23 g, 5.15 mmol, yield 9).
6%).

Elemental analysis Calculated value for C ₃₂ H ₅₄ Cl ₂ FeP ₂ (%) C61.25 H8.67 Actual value (%) C61.25 H8.65 Magnetic moment μ _eff = 4.99 BM

Example [Synthesis of Fe (η ⁶ -naphthalene) (dtype)] FeCl ₂ (dtype) (2.03 g,
3.24 mmol) of tetrahydrofuran (hereinafter TH)
F) solution (22 mL) was added dropwise a solution of sodium naphthalenide (55 mL, 15.0 mmol) in THF at room temperature under an argon atmosphere. After reacting at room temperature for 23 hours, the solvent was distilled off and dried. The resulting dark green tar was extracted with hexane (140 mL). Volatiles were removed under reduced pressure. The resulting solid was recrystallized from cold hexane ^{(70mL), Fe (η 6} - naphthalene) (dcype) · 0.5C ₆ dark green crystals (yield 0.593g of H _14, 0.977 mmol, yield 30%).

Melting point 166-167 ° C (decomposition) Elemental analysis Calculated value for C ₇₈ H ₁₂₆ Fe ₂ P ₄ (%) C 72.10 H 9.77 Actual value (%) C 71.67 H 9.33

¹ H NMR (C ₆ D ₆ ): δ 4.20, 5.69 (br, 4H,
coord.ring, C ₁₀ H ₈ ), 7.09, 7.41 (m, 4H, uncoord.r
ing, C ₁₀ H ₈ ) ¹³ C ｛ ¹ H｝ NMR (C ₆ D ₆ ): δ59.99, 79.46 (s, coord.ri
ng, C ₁₀ H ₈ ), 97.62 (s, ring junction, C ₁₀ H ₈ ), 121.0
7, 126.89 (s, uncoord. Ring, C ₁₀ H ₈ ) ³¹ P ｛ ¹ H｝ NMR (C ₆ D ₆ ): δ94.60 (s)

Test Example (Synthesis of Tetralin) Fe (η ⁶ −
Naphthalene) (dtype) (0.1362 g, 0.2
(25 mmol) was dissolved in THF (12 mL). This dark green solution was transferred to an autoclave (internal volume 50 mL, with a glass liner) using a catheter tube, and hydrogen pressure 2
The mixture was stirred at 0 atm at room temperature for 20.5 hours. After completion of the reaction, the solvent was distilled off under reduced pressure from the brown reaction solution under an argon atmosphere, and the mixture was extracted with hexane (23 mL). The extracted solution was filtered through a glass fiber filter paper, the solvent was again distilled off, and the residue was dried under vacuum to obtain Fe (η ⁶ -tetralin) (dcy).
pe) (yield 0.1220 g, yield 9)
0%).

When this brown powder was recrystallized (−20 ° C.) from hexane (3 mL), Fe (η ⁶ -tetralin) was obtained.
(Dtype) was obtained as brown cube-shaped crystals. Elemental analysis Calculated value for C ₃₆ H ₆₀ FeP ₂ (%) C70.81 H9.90 Actual value (%) C70.05 H9.53

¹ H NMR (300 MHz, C ₆ D ₆ ): δ1.04-2.22
(m, 48H, aliphatic protons of PCH ₂ and Cy), 2.82
(br, 4H, CH ₂ of uncoordinated ring), 3.67, 5.60 (b
r, 4H, CHof coordinated ring) ³¹ P ｛ ¹ H｝ NMR (C ₆ D ₆ ): δ 99.13 (s) IR (KBr, cm ^-1 ): 2924 (s, CH), 2847 (s, CH), 14
45 (s, PC), 1261 (s, C = C)

[0026]

As described above, the zero-valent iron complex of the present invention is
There is an effect that tetralin or its derivative can be easily produced by regioselective partial hydrogenation of naphthalene.

Claims (7)

[Claims] (1) Formula (1): (Where Cy represents a cyclohexyl group, R represents a lower alkyl group, and n represents an integer of 0 to 8). 2. Fe (η ⁶ -naphthalene) (dtype)
2. The iron zero-valent complex according to claim 1, wherein dtype is 1,2-bis (dicyclohexylphosphino) ethane. 3. An iron (II) chloride complex represented by the formula: FeCl ₂ (dtype), wherein dtype represents 1,2-bis (dicyclohexylphosphino) ethane, is represented by the formula: C ₁₀ H _{8 -n} R _n Na (wherein, R is a lower alkyl radical, n represents. an integer of 0 to 8) which comprises reducing with sodium naphthalenide or a derivative represented by claim 1, wherein Expression
A method for producing a zero-valent iron complex represented by (1). 4. The method according to claim 3, wherein the reduction is performed in a solvent under an inert gas atmosphere. 5. An iron (II) chloride complex comprising iron (II) chloride and 1,1
The method according to claim 3, which is obtained by reacting with 2-bis (dicyclohexylphosphino) ethane. 6. The iron (0) complex represented by the formula (1) according to claim 1 is reacted with hydrogen to obtain a compound of the formula (2): (Wherein Cy represents a cyclohexyl group, R represents a lower alkyl group, and n represents an integer of 0 to 8), wherein tetralin or a complex having a derivative thereof as a ligand is obtained. Manufacturing methods. 7. The reaction is carried out at a hydrogen pressure of 5 to 40 atm and 0
The method for producing tetralins according to claim 6, which is carried out at a temperature of -50C.